The browser is only one point of entry. Even linux distros have holes in them. Be careful with a false sense of security. Always stay up to date, moreso than relying on being on a linux distro.

Agreed. Running linux just means there is fewer viruses that are gunning for you. I'm a fan of layers, so I run Comodo to keep an eye out for virus/malware. My next step is to get set up with a VPN service. With that setup I become a small target, somewhat obscured from view and with a kevlar vest on.

I like my chances.

vpn doesn't really do much, if you want, setup your own. Get a server for $5/mo and slap openvpn for your own private vpn, if you use a paid service you're open to man-in-the-middle attacks. Security is all about layers.